Shell molding apparatus



3, 1959 T. L. BURKLAND SHELL MOLDING APPARATUS 2 Sheets-Sheet 2 Filed June 1, 1954 FIG. 5

INVENTOR. THEODORE L. BUR/(LAND Unite SHELL MOLDING APPARATUS Application June 1, 1954, Serial No. 433,385

Claims. (Cl. 22-90) The present invention relates generally to molding apparatus and is particularly concerned with new and useful improvements especially adapted for use in the so-called shell molding process.

In the shell molding process, the desired casting is formed by pouring molten metal between two mold shells. The mold shells are made by applying a mixture of sand and resin over a permanent pattern, usually made of cast iron, and, through the use of heat, forming the desired mold shell on the metal pattern by baking or curing, after which the mold shell becomes a rigid part and can be removed whole from the pattern and stored for use later in the casting operation.

The object and general nature of the present invention is the provision of new and improved means for backing up the mold shells, which are relatively easily fractured, with suitably formed backing plates or members that are so constructed and arranged to apply pressure against the outer or back sides of the mold shell sufficient to retain them in position against the pressure of the molten metal during the pouring or casting operation.

More specifically, it is a feature of this invention to provide a new and improved back-up plate structure having cavities formed therein so as to clear all outwardly projecting parts of the mold shell but arranged to contact the flat portions of the shell, particularly those portions that are brought together against the corresponding portions of the opposite shell to complete the mold cavity in which molten metal is poured. In thisway, by contacting only the flat portions of the mold shell, there is little likelihood of fracturing the shells when the frames carrying the shells are clamped together just prior to the pouring step.

Additionally, it is a further feature of this invention to provide new and improved means for holding the back-up plates in the proper position relative to the mold shells and a new and improved means for applying a resilient pressure against the back-up plates so that, when necessary, irregularities at the outer or back sides of the mold shells may be tolerated.

These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description of the preferred structure in which the principles of the present invention have been incorporated.

In the accompanying drawings:

Fig. 1 is a front elevational view of mold shell clamping and supporting structure in which the shells are maintained in the position necessary to accommodate the pouring step.

Fig. 2 is an end view of the structure shown in Fig. 1.

Fig. 3 is an enlarged plan view of the upper shellcarrying frame, showing three of the back-up plates in operative position.

Fig. 4 is a side view of the frame and associated parts shown in Fig. 3.

2,3?1531 Patented Feb. 3, 1959 Fig. 5 is an end view of the frame structure shown in Fig. 3.

Fig. 6 is an enlarged sectional view, taken generally along the line 66 of Fig. 3.

Fig. 7 is a fragmentary View taken along the line 77 of Fig. 3, showing the way in which the backing plates hold the mold shells in their proper position for pouring.

Referring first to Figs. 1 and 2, the reference numeral till indicates a support in the form of a vertical framework that includes a pair of side channels 11 and an upper cross channel 12 suitably connected together to secure the necessary rigidity. The lower ends of the channels 11 have base angles 13 connected in any suitable way, as by brackets 14 and strut members 15,

with the side channels 11. A carriage 21? is movable generally vertically between the side channels 11 and includes outwardly extending arms 21 connected by gusset plates 22 to a cross channel 23, all rigidly interconnected, with operating means in the form of a ram .255 that includes a cylinder 26 fixed at its upper end to the frame channel 12 and a piston rod 27 connected at its lower end with the channel 23 of the carriage 20.

The carriage 2% is movable generally vertically by operation of the ram 25, and the carriage 20 supports the upper frame In; that, with associated parts, forms a means supporting the upper shell that is formed according to the shell molding process. A similar frame 31, supporting a lower mold shell, is carried by a platform structure 33 that is made up of vertical and horizontal members as and 35 of any suitable construction. The horizontal members 35 carry journal boxes 36 in which the trunnions 37 of the lower frame 31 are received. The upper frame 39 is provided with similar trunnions 38 rockably received in the outer ends of the carriage arms 22.

The upper and lower frames 3%} and 31 are of substantially identical construction, and hence a detailed description of one will sufiice.

Referring now to Figs. 36, the upper frame 3Q comprises a pair of end channels 4 the flanges of which are interconnected by a vertical plate 42 to which the trunnions 38 are secured, as by welding or the like. The inner ends of the trunnions 38 are also secured to the webs of the end channels 4-1. Each of the sides of the frame 383 comprises a lower angle member 44 and an upper channel member 45 arranged as best shown in Fig. 5. The webs of the channel members 45 are apertured at a plurality of points, as indicated in Fig. 3, to receive a plurality of spring-biased pins 4-7. Each of these mem hers is preferably in the form of a short bolt 48 having a head 4? against which a spring 51 bears, the upper end of the spring contacting the lower face of the web of the associated channel 45. The upper end of the bolt 48 carries a nut 53 which limits the permissive downward movement of the bolt i8. Attachment of the ends of the upper channels 45' to the end channels 41 is preferably effected through attaching plates 55 that are apertured to receive connecting bolts 56, the plates 55 being welded or otherwise secured to the ends of the upper channels 45. As best shown in Pig. 3, a multiplicity of the springbiased pins or bolts are provided at each side of the upper frame 30.

The lower flange of each of the lower side angles 44 is also provided with a plurality of apertures in which a plurality of-studs or pins 5'8 are fixedly secured.

Each of the frames 30 and 31 is constructed, as described above, to receive one or more shell-clamping members 60. Each of these members is in the form of a backing or back-up plate that usually is constructed as a casting 6i, and the form and shape of the back-up members or plates 61 is determined, of course, by the o mold shells with which the back-up plates are particularly adapted to cooperate. Referring now to Fig. 7, two of the mold shells, in a position to receive the molten metal, are indicated at 65 in this figure. The size, shape and configuration of the mold shells 65 depend, of course, upon the particular casting it is desired to form, but generally the mold shells include contacting marginal sections 66 and laterally outwardly extending sections 67, 68, 69, etc. in which the molten metal is poured, as

through a gate section '71. Depending upon the shape of the casting desired, the mold shells 65 have fiat portions 72 and these may or may not contact one with the other but, in any pair of mold shells, there are always some flat contacting sections, as indicated at 66, usually at the marginal portions of the mold shells but sometimes also at the intermediate portions. The mold shells are relatively hard and rigid and are capable of being handled, but at the same time they are also frangible in that they can be broken, for example, by a hammer blow or by substantial internal pressure.

One of the principal features of the present invention is the provision of the back-up plates 61, so constructed and arranged that they bear chiefly on the flattened portion 66 of the mold shells, which portions are usually in mutually contacting relation, but clear the other portions of the mold shell, particularly the outwardly extending parts with StlfllClfilll'. space so that notwithstanding some irregularity in the outer contours of the mold shells, the back-up plates 61 never forcibly come into contact with the outer walls of the mold shells except at those portions in which the mold shells contact one another. In order to achieve this result in the construction shown in the drawings, each of the back-up plates 61 is shown as incorporating a plurality of through openings 76 that clear the associated outwardly extending portions of the mold shells with sufiicient space so that when the back-up or clamping members 61 are disposed against the outer or back sides of the assembled mold shells, no portion of the back-up plates is permitted to forcibly contact the outer surface of the mold shell and fracture it, yet, as shown in Fig. 7, the back-up plates engage the flat contacting portions of the shells so as to effectively support the latter during the pouring step. In cases where, as shown at 72 in Fig. 7, for example, where the non-contacting portions of the shell are flat, the corresponding portions of the back-up plates 61 are also formed generally flat but with sufficient clearance to take care of variations in thickness of the mold shell.

As will best be seen from Fig. 3, therefore, each of the back-up plates 61 comprises a clamping member having cavities or openings therethrough to accommodate the outwardly extending portions of the associated mold shells whereby one of the flat or contacting portions of the mold shells is engaged by the backing or clamping members 61. Clamping pressure against the plates 61 is secured in the following manner.

The members 61 are castings, generally speaking, and, as will be understood by those skilled in the art, the dimensions of the castings cannot be held to the close tolerances or limits that would be desired, especially in shell molding, yet the clamping members 61 must be accurately positioned relative to the associated pair of mold shells. In order to thus provide for the desired close tolerances, I first provide tapped openings 31 in the backing members 61 and thread into each of the openings'sl a stud 82. Then in a suitable fixture (not shown), and with the members 61 in the necessary position therein, I provide a plurality of bars 84 the outer ends of which are disposed against gauging surfaces, and weld such bars 84 to the associated pins 32, as best shown in Fig. 6. In this way, notwithstanding variations in the shape and dimension of the castings 61, the pins 84 rigidly con nected thereto effectively and invariably locate the castings 61 in the proper position in the associated frame, 30 or 31. For guiding and maintaining the clamping iii) 6 members 61 in the proper position, the bars 84 are disposed between the pins 58 on the lower angles 44, with the spring-biased pins 49 engaging the upper edges of the bars 84. Thus, when the ram 25 is operated to force the carriage 2t) downwardly, forcing the frame 36 against the frame 31, yielding resilient pressure is applied against the bars 84 of the upper clamping member 61, and, through the marginal portions of the latter and the associated flat section 66 of the contained mold shell 65, pressure is exerted against the lower member 61, which pressure is cushioned by the spring-biased members associated with the lower frame 31.

During the pouring step, the mold shells are destroyed, and after the castings have hardened in the shells, which occurs before their being burned out, the upper frame is raised relative to the lower frame and the castings and associated debris are dumped out, after which the next pair, usually a plurality of pairs, of shell molds are brought into position underneath the clamping members and the operation repeated.

While I have shown and described above the preferred structure in which the principles of the present invention have been incorporated, it is to be understood that the present invention is not to be limited to the particular details shown and described above, but that, in fact, Widely different means may be employed in the practice of the broader aspects of my invention.

What I claim, therefore, and desire to secure by Letters Patent is:

1. For use in the shell molding process, wherein castings are made by pouring molten metal into the space between a pair of mold shells that have flat portions disposed in contact with one another and other portions that extend outwardly at the back side of the shell, a backing plate structure comprising a relatively heavy part formed with cavities, shaped to clear the outwardly extending portions at the back of the shell, other portions which are generally flat at their shell-engaging surface and shaped to engage the portions of the associated shell that contacts the corresponding portions of the opposite mold shell, and extensions at opposite margins of said backing plate structure, and resilient means acting against said extensions for urging said plate structure toward the associated mold shell.

2. Molding apparatus comprising a lower relatively fixed support, an upper support carried for movement toward and away from said lower support, an upper frame carried by said movable support, a lower frame carried by said relatively fixed support, each frame including an inner section and an outer section, a back-up plate structure carried in each frame and each having a plurality of laterally outwardly extending parts, guiding means on the inner section of the associated frame for receiving and guiding said parts, and spring biased means carried by each outer framesection and positioned so as to engage the outwardly extending parts of the associated back-up plate structure, said spring biased means acting in a direction to urge said back-up plate structure toward said inner frame structure, said upper frame being carried in said movable support with the asso ciated back-up plate structure facing and urged downwardly by the associated spring biased means, the lower frame being carried in said lower relatively fixed support with the associated back-up plate structure facing and urged upwardly by the associated spring biased means, and means connected with said upper movable support for moving the upper frame and the plate structure carried thereby toward the other frame and the plate structure associated therewith whereby said plate structures are adapted to clamp mold shells therebetween, each back-up plate structure being yieldably urged against said mold shells by said spring biased means.

3. Molding apparatus comprising an upper frame, a lower frame, each frame including an inner section and an outer section, a plurality of positioning. pins carried by the inner section and extending toward the outer section, a back-up plate structure carried in each inner section and each back-up plate structure disposed within said positioning pins and having a plurality of laterally outwardly extending parts adapted to be disposed between the positioning pins of the associated inner frame section into the space laterally outwardly thereof, and a plurality of spring biased pins rnovably carried by each outer frame section and positioned laterally outwardly of said positioning pins so as to engage the outer ends of said outwardly extending parts of the associated back-up plate structure, and means connected with one of said frames for moving the latter and the plate structure carried thereby toward the other frame and the plate structure associated therewith, said spring biased pins serving to yieldably hold said back-up plate structures in closed relation.

4. For use in the shell molding process, a mold shell clamping fixture comprising a pair of frames, means forcing one of said frames toward the other, spring biased means carried along each of two opposite sides of each frame, at least one pair of rigid shell backing plates carried respectively by said frames, each plate having at least one pair of projections extending outwardly from opposite ends of said plate and adapted to be engaged by said spring biased means and resiliently urged toward the other plate when the frames are closed, and guide means carried by each frame and engageable with said backing plate projections for holding the backing plates in position in the associated frames.

5. For use in the shell molding process, a mold shell clamping fixture comprising a pair of frames, means forcing one of said frames toward the other, a plurality of spring biased pins carried by each frame in uniformly spaced apart relation, a plurality of guide pins also carried by each frame and spaced apart the same as said 5 spring biased pins but arranged in staggered relation with respect to said spring biased pins, and at least one pair of rigid shell backing plates carried respectively by said frames, each plate having at least one pair of projections extending outwardly between the associated guide 10 pins so as to be engaged by one of said spring biased pins and resiliently urged toward the other plate when the frames are closed, whereby when the frames are closed portions of said plates act to engage associated portions of the shell molds, other portions of said back- 15 ing plates being formed so as to clear outwardly lying parts of the molds.

References Cited in the file of this patent UNITED STATES PATENTS Foundry, September 1952, pages 108-111. American Foundryman, vol. 24, issue 1, page 51, July 1953, Dietert Process for Precision Molds. 

